1. Field of the Invention
The present invention relates to a network control system for offering a plurality of remote services such as chat (electronic dialogue), distribution of data (mail), RCS (remote computer service) and processing for a non-attendant subscriber.
Recently, it has been considered to execute processing while realizing communication with remote terminal units through a communication network and it is therefore desired to effectively utilize the communication line for this purpose. Moreover, for communication within the public network or in the network coupling the public network and private network, a low cost communication network may have enough capacity in some cases for use in connection profile of networks. However, when for instance a large amount of images are transmitted as in recent communications, reduction of communication cost becomes a very important problem. In addition, if a distant subscriber is absent, it is now desired to provide a system which can urgently call the distant subscriber.
2. Description of the Related Art
Recently, a communication network has grown more and more complicated as shown in FIG. 29. Namely, certain terminal units are connected with a public network and certain terminal units are coupled with a private line (so-called private leased line network) and these terminal units are capable of communicating a variety of information including image information.
FIG. 29 shows an example of the network. In this figure, the numeral 1 denotes public network; 2, private line; 10A, 10B, 10C, 10D, groups respectively; 3A, 3B, 3C, 3D, terminal units as control stations; 4A, 4B, 4C, 4D, ordinary terminal units respectively.
The terminal units 3A and 4A, 3B and 4B, etc. are connected with the same communication network and are regionally adjacent and thereby classified into the groups 10A, 10B, etc.
In each group, at least one terminal unit functioning as control station 3A, 3B, etc. is provided and some control stations are connected with both the public network 1 and private line 2.
Under the network as shown in FIG. 29, it has been recently desired to execute a plurality of remote services between terminal units, such as chats, message distribution (mail), RCS (Remote Computer Service) and processing for the distant subscriber who is absent. It is certainly desired to realize the remote service as explained above but the following problems arise.
Namely, in the prior art, since the communication line is continuously set open during the services, a dead time when transmission and reception are not directly carried out is also part of the communication cost. Moreover, to avoid such cost, it has been considered to open or close the communication line. However, in this case, an operator must take part in the operation.
Moreover, an application charge of a public network is not proportional to application distance. The application charge in a certain application area may sometimes be higher than the sum of the charge to a certain intermediate point and the charge to the target point from such intermediate point. However, in this case, an application profile in which the charges are lowered, for example, by employing a repeating means does not presently exist now.
Moreover, even in a case where a plurality of long-length distant terminal units for transferring data are distributed and the distant terminal units are located very closely, it is necessary to individually send data through long-length communication to respective distant terminal units.
Private lines have been provided for reduction of communication cost. It is desired to create a connection profile taking advantage of the cost merit of private line while also taking advantage of the nation wide scale of the public network considering the conditions of respective terminal units for making communication to terminal units on the public network from terminal units connected to such private line, or to terminal units on the private line from that of the public network.
Furthermore, realization of message distribution (mail) introduces the following problems.
FIGS. 30(a) and (b) schematically show systems as in the prior art for distributing real data to other terminal units (receiving station) 122-124 from one terminal unit (transmitting station) 121. In FIG. 30(a), the transmitting station 121 transmits the real data, for example, conference proceedings to be circulated to the first receiving station 122 and this receiving station 122 confirms and processes the contents of data received and then returns it to the transmitting station 121. When the transmitting station 121 confirms existence of the data returned from the first receiving station 122, it transmits such returned data to the second receiving station 123 and the second receiving station 123 also confirms and processes contents of data in the same way as explained above and then returns the data to the transmitting station 121. Such method is repeated, for example, for the stations after the third receiving station 124 to sequentially distribute real data from the transmitting station 121.
In the case of FIG. 30(b), when the transmitting station 121 transmits real data to the host center 130, this host center 130 then functions in place of the transmitting station 121 to send or receive the real data sequentially with the receiving stations 122-124.
In such prior art, after a certain receiving station receives real data, the real data checked and processed is always returned to the transmitting station and it is then transmitted to the next receiving station. The real data therefore goes forward and then backward through the communication path. As a result, a problem arises that since application of line becomes ineffective and the information system in the transmitting station or the host center must always be operated, the other necessary processings in the transmitting station are set in a queue condition.
In addition, realization of RCS explained above also introduces the following problems.
FIG. 31 is a diagram for explaining the prior art indicating the inter-terminal communication.
In FIG. 31, 201 denotes a predetermined terminal; 202 (202-1 -202-6), terminal units other than the predetermined terminal unit 201 (ordinary terminal unit); 215, switching equipment and communication network (or public network).
Communication between terminal units 202 is carried out, as shown in FIG. 31, through the predetermined terminal unit 201. The predetermined terminal unit 201 is a computer (hereinafter referred to as host) determined as host for communication between terminal units in this network.
For example, when the terminal unit 202-1 wants to start communication with the terminal unit 202-3, the following processes are carried out. First, the request issuing terminal unit 202-1 connects the line to the host 201 through the switching equipment and communication network 215 and notifies the terminal unit number of the terminal unit 202-3. The host 201 knows the telephone number of the terminal unit 202-3 from this terminal unit number and connects the line to the terminal unit 202-3 through the switching equipment and communication network 215. Thereafter, data transfer is carried out between the terminal units 202-1 and 202-3. First, data is sent, for example, to the host 201 from the terminal unit 202-1 and this data is then sent to the terminal unit 202-3 from the host 201. Therefore, the host 201 executes the processing (data-through processing) to send the data received from the line connected to the terminal unit 202-1 to the line connected to the terminal unit 202-3.
When communication to the terminal unit 202 is carried out through the data-through processing executed by the host (predetermined terminal unit) 201 as explained above, however, the following problems are generated.
As shown in FIG. 31, a plurality of communications such as communication between terminal units 202-1 and 202-3, communication between terminal units 202-2 and 202-4 and communication between terminal units 202-5 and 202-6 are carried out almost simultaneously to the host 201. In this case, it is necessary to conduct the data-through processing by processing respective communication requests, but the resultant load becomes heavy for the host 201. Accordingly, it is probable that the host 201 can no longer execute the other processes. On the contrary, since the host 201 is not a switching equipment but a computer, the number of connecting lines and the switching function are restricted. Therefore, if the communication requests are concentrated at one time, communication becomes impossible in some cases.
During the processing conducted when the distant subscriber is absent, the following problems are also encountered.
In the case of asking an operator to search a supervisor of the absent terminal unit, the situation becomes troublesome because the supervisor is requested to previously notify the destination to the operator of its own terminal unit. Moreover, if the supervisor has forgotten to notify the destination to an operator, a problem occurs that it is no longer possible to find out the destination of the supervisor. In the case of searching for the destination of the supervisor by utilizing an absent transfer function of the telephone set, a problem also rises that if the destination of the supervisor changes from time to time, it is also impossible to find out the destination of the supervisor. Namely, the absent terminal unit is not provided with a function to make communication with the transmitting other terminal units and furthermore is not provided with a function to search the supervisor.